The present invention relates generally to a method and apparatus for the installation of a liner within the interior of such a conduit or pipe, such as a sewer pipe.
It is generally well known that the conduits or pipes, particularly underground pipes, which are employed for conducting fluids, for example, sanitary sewer pipes, storm sewer pipes, water lines and gas lines, frequently require repair due to fluid leakage. The leakage may be inwardly, from the environment into the interior or conducting part of the pipe, or outwardly, from the conducting part of the pipe into the surrounding environment. Leakage of this type may be due to improper initial installation of the pipe, deterioration of the pipe itself due to normal aging or the effects of conveying corrosive or abrasive materials, cracking of the pipe or pipe joints due to environmental conditions such as earthquakes, the movement of large vehicles or similar natural or man made vibrations, or any other such causes. Regardless of the cause, such leakage is undesirable at best and may result in waste of the fluid being conveyed by the pipe, damage to the surrounding environment and the possible creation of dangerous public health hazards.
Because of ever increasing labor and machinery costs, it is becoming increasingly more difficult, at least economically, to dig up and replace underground pipes or portions or sections of such underground pipes which may be leaking. As a result, various methods have been devised for the in situ repair or rehabilitation of the existing pipes, thereby avoiding the expenses and hazards associated with digging up and replacing the pipes or pipe sections. One of the more successful pipe repair or rehabilitation processes which is currently used is called the Insituform process and is described in U.S. Pat. Nos. 4,009,063; 4,064,211; and 4,135,958 the contents of which are incorporated by reference herein.
Briefly, in the Insituform process, an elongated flexible tubular liner comprised of a felt fabric or foam or similar flexible material, which has been impregnated with a thermosetting synthetic catalyzed resin is installed within the existing pipe utilizing an inverting or everting process as described in the aforesaid patents. Once the flexible liner is installed in place within the pipe, the liner is pressurized from within, preferably utilizing a fluid such as water, to force the liner radially outwardly to engage and conform to the interior surface of the pipe and to force some of the impregnated resin into any cracks or interstices within the walls of the pipe. The resin is then cured to form a relatively hard, tight fitting, rigid pipe lining which effectively seals any cracks and repairs any pipe or pipe joint deterioration to prevent further leakage either into or out of the pipe. The cured resin liner also serves to strengthen the existing pipe walls to provide added structural support for the surrounding overburden.
The method described in the aforementioned U.S. patents for inserting the liner into the pipe involves the use of a tower or scaffold which is approximately twenty-five to thirty feet high in order to provide the necessary water pressure head required to invert the liner and push it along the length of the pipe to be lined. While this method has been successfully utilized, it is relatively expensive in terms of both equipment and manpower to erect and operate such a large structure. In addition, such a large structure is awkward to utilize and, due to the height and the use of very hot water within the elevated structure to cure the resin, is dangerous to the operating personnel. Moreover, the existing liner insertion method is inadequate especially for the installation of a liner into a large diameter pipe since no positive control of the insertion and inversion of the liner is provided throughout the entire inversion process. In addition, it is difficult to work with the tremendous forces that are created by the water pressure required for such a large liner installation.
The present invention overcomes many of the difficulties inherent in the prior art liner installation method by providing a relatively self-contained, mobile system which permits the use of air pressure in combination with, and in some instances in lieu of, water pressure for the installation and inversion of the liner. In this manner, the liner can be installed within the pipe without the need for a large tower and without the need for numerous operator personnel. The present invention also provides for effective, positive, continuous control of the rate of insertion of the liner as it is being installed within the pipe and, therefore, the present method and apparatus is adapted for use in connection with the installation of liners in pipes of differing diameters without the need for additional equipment or personnel.